With an increasing number of electric parts being mounted on automobiles, a larger amount of electric power is required to operate the electric parts. A large capacity generator or battery is required in order to secure a power supply for them. The generator is driven by power from the engine. Accordingly, an increase in power supply causes reduction in fuel economy. In automobiles, a large amount of heat energy is discharged from driving force generating devices such as an engine and a motor. Accordingly, attempts have been made to generate electric power by using exhaust heat of the engine etc.
For example, Patent Document 1 discloses an energy recovery device having a thermoelectric element placed on the back surface of an engine hood. Patent Document 2 discloses an exhaust gas heat sink including a thermoelectric element. Patent Document 3 discloses a vehicle in which a temperature difference secondary battery using a redox couple is attached to an engine to generate electric power. Patent Document 4 discloses a power generation device using residual heat, which transfers heat from an engine to a thermoelectric element via a heat pipe to generate electric power.